Applications of the extrinsic Fabry-Perot interferometer

We discuss two of the latest demonstrations of the extrinsic Fabry-Perot interferometer (EFPI) sensor, namely a novel silica fiber-based hydrogen sensor and a high-temperature, sapphire fiber-based displacement sensor for surface strain measurements at temperatures up to 2000 degrees C. To modify the EFPI sensor for the detection of hydrogen, the sensor is sputter coated with a 2 micrometers layer of palladium. Based on the signal-to-noise ratio of the sensor, a minimum detectable hydrogen concentration of 35 ppm has been obtained. For displacement measurements at temperatures above the melting point of silica, we discuss results using a sapphire fiber EFPI sensing head demodulated using white light scanning Michelson interferometer.